IMGD 1001: 3D Art by Mark Claypool (claypool@cs.wpi.edu) Robert W . - PDF document

IMGD 1001: 3D Art by Mark Claypool (claypool@cs.wpi.edu) Robert W . Lindem an (gogo@wpi.edu) Outline � The Pipeline � Concept Art � 2D Art � Animation, Tiles � 3D Art (next) � Modeling, Texturing, Lighting, Transformations Claypool & Lindeman - WPI, CS & IMGD 2 1

Polygonal Modeling Basics: Primitives � Primitives are basic shapes � Most 3d packages have same primitives: � Sphere, Cube, Cylinder, Plane � Use for “broad strokes” � Concentrate on primitives within object � Ex: human body (ovals for shoulders, cylinders for legs, sphere for head… ) � Components are parts that make up primitive � Ex: vertices, edges, triangles, faces, elements � Similar across all packages but terminology can vary � Transformation allows moving, rotating, scaling object or component Claypool & Lindeman - WPI, CS & IMGD 3 Polygonal Modeling Basics: Normals � Face normals are at right angle to polygon � Tell what direction if facing, how to render, how light will react � Viewed from other side, is invisible � Fine if on inside (say, of solid cube) � When debugging, pay attention to normals as well as polygons Claypool & Lindeman - WPI, CS & IMGD 4 2

Polygonal Modeling Basics: Backface Culling � Toggles display of faces that point away from view � When on, see through wireframe � When off, looks solid (not drawn) � Makes look less cluttered Claypool & Lindeman - WPI, CS & IMGD 5 Modeling Tools � Certain tools and techniques used 80-90% of the time � Line Tool : � Draw outline of object and extrude to get 3-d shape � Ex: profile of car. Use line tool. Then, extrude outward to get shape. � Extrude : � Take component (often face), duplicating it, pulling pushing or scaling to refine model � Ex: take cube. Extrude face outward and smaller � Cut : � Subdivides faces and adds new faces � Adjust : � The artistic part of modeling. Try to capture form, profile and character by moving vertices � “Vertex surgery”, part of the technical manipulation Claypool & Lindeman - WPI, CS & IMGD 6 Based on Chapter 6.2, Introduction to Game Development 3

1 Modeling Technique: Box Modeling � Done for character, but can apply to other things � General idea: � Start with box, cylinder or other primitive � Extrude, Cut, Adjust… � Get topology, proportions right � Once happy, refine until details complete Claypool & Lindeman - WPI, CS & IMGD 7 Box modeling: Quick Example � Reference � Box modeling: extrude, cut, adjust � Compare to reference � Shade Claypool & Lindeman - WPI, CS & IMGD 8 Based on Chapter 6.2, Introduction to Game Development 4

Polygons and Limits � 3d Software renders scene of polygons like game � But 3d software slow ( Toy Story 1 frame / 15 hrs) � Game is real time (30 frames / second) � Need to limit polygons. How spent depends upon world size and where needed. � Ex: Medal of Honor versus Soul Caliber 2 . MoH details spread across world, less on avatars. SC2 can have detailed avatars since only 2 in one ring. � Think of how many polygons each item needs. Estimates, educated guesses. Then, make pass. (Tools will often give count) � Used wisely, can make detailed scenes with few (Ex: 2.5, page 24) � Ch 6.2 assumes 4000 (typical for PS2 street fighting game or hero in 3 rd person action game) Claypool & Lindeman - WPI, CS & IMGD 9 Based on Chapter 2, Creating the Art of the Game , by Matthew Omernick Polygon Reduction (1 of 4) � Being able to model without wasting polygons important � takes practice � Ask if a player will see face? � Ex: oil barrel as cylinder. Will see bottom? Nope, then delete. � Are all faces necessary? Looks great, yeah, but some can be removed. � Ex: 12-sided cylinder still looks “round” with 8 sides? Then do it. � (Example exercise p30-31) Claypool & Lindeman - WPI, CS & IMGD 10 Based on Chapter 2, Creating the Art of the Game , by Matthew Omernick 5

Polygon Reduction (2 of 4) � Level-of-detail (LOD) meshes � Multiple versions of object, progressively lower levels � When far away, use low level � Assume more objects in Field of View � When close, use higher level � Assume fewer objects in Field of View Claypool & Lindeman - WPI, CS & IMGD 11 Polygon Reduction (3 of 4) � For entire level (ie- map with environment), entire polygon count matters � Impacts amount of memory needed � But only visible polygons rendered � Rest are “culled” and not computed Images courtesy of WildTangent Claypool & Lindeman - WPI, CS & IMGD 12 Based on Chapter 6.2, Introduction to Game Development 6

Polygon Reduction (4 of 4) � With low polygon modeling, much of the detail is painted into the texture (next topic!) Images courtesy of WildTangent, model and texture by David Johnson. Claypool & Lindeman - WPI, CS & IMGD 13 Based on Chapter 6.2, Introduction to Game Development Texture � Shader – define surface property of object – how shiny, bumpy, how light effects � Texture – bitmap plugged into shader that defines image we want to appear on object Claypool & Lindeman - WPI, CS & IMGD 14 Based on Chapter 6.4, Introduction to Game Development 7

Detail in Texture � Add depth, lines, etc. without polygons � Box is 12 polygons, bricks would take many more (Taken from http://www.mostert.org/3d/3dpdzscenem.html) Claypool & Lindeman - WPI, CS & IMGD 15 Based on Chapter 6.4, Introduction to Game Development Lighting � Can conjure feelings, emotions, even change what you are seeing � Reveal (or hide) depth � (Many books on traditional lighting) � AR/ ID 3150. LIGHT, VISION AND UNDERSTANDING � Color, Mood Claypool & Lindeman - WPI, CS & IMGD 16 Based on Chapter 6.6, Introduction to Game Development 8

The Role of Color RTX Red Rock Color indicates danger Claypool & Lindeman - WPI, CS & IMGD 17 http://www.informit.com/articles/article.asp?p=174370 The Role of Lighting Long shadows not only add to the atmosphere, but also help break up repetition Claypool & Lindeman - WPI, CS & IMGD 18 http://www.informit.com/articles/article.asp?p=174370 9

Lighting Setup (1 of 3) Key light – main source. The Key light is placed next to the camera, about 35-45 degree angle to the subject. The angle is determined by what kind of mood that you want the scene to have. Claypool & Lindeman - WPI, CS & IMGD 19 http://www.3dtotal.com/team/Tutorials/Jenns3pt_tut/3ptlighting.asp Lighting Setup (2 of 3) Fill light – Brings out some details out of shadow. Place the Fill Light at a 90 degree angle from the Key Light, usually slightly higher or lower than the Key Light. Claypool & Lindeman - WPI, CS & IMGD 20 http://www.3dtotal.com/team/Tutorials/Jenns3pt_tut/3ptlighting.asp 10

Lighting Setup (3 of 3) Backlight - Highlights edges, pulls away from background. Placed directly opposite the camera and behind the subject. Claypool & Lindeman - WPI, CS & IMGD 21 http://www.3dtotal.com/team/Tutorials/Jenns3pt_tut/3ptlighting.asp Working with 3D Lights � Directional Lights – used for sunlight or moonlight. Often as key light. Predictable. � Ambient Lights – spread everywhere, equally. Uniform diffuse lights. Precise control over illumination. � Spot Lights – focus beam on single location. Great control. � Point Lights – single point in all directions. Light bulbs, candles, etc. Claypool & Lindeman - WPI, CS & IMGD 22 Based on Chapter 6.6, Introduction to Game Development 11

Example of Working with 3D Lights Ambient light Claypool & Lindeman - WPI, CS & IMGD 23 Based on Chapter 6.6, Introduction to Game Development Effective Lighting Practices (1 of 2) Pools of light – Don’t always try to light evenly. - Gives sense of mystery Pools of light in Indiana Jones: The Emperor's Tomb Claypool & Lindeman - WPI, CS & IMGD 24 Based on Chapter 6.6, Introduction to Game Development 12

Effective Lighting Practices (2 of 2) Guide lights – - Use light to guide the player. - Helps highlight areas that are accessible and important to the objectives. Claypool & Lindeman - WPI, CS & IMGD 25 Based on Chapter 6.6, Introduction to Game Development Introduction to Transformations � A transformation changes an object's � Size (scaling) � Position (translation) � Orientation (rotation) � Transform object by applying sequence of matrix multiplications to object vertices Claypool & Lindeman - WPI, CS & IMGD 26 13

Hierarchical Transformations � Graphical scenes have object dependencies � Many small objects � Attributes (position, orientation, etc. ) depend on each other hammer A Robot Hammer! lower arm base Claypool & Lindeman - WPI, CS & IMGD 27 Hierarchical Transformations � Object dependency description using tree structure Root node Base Object position and orientation can be affected by its parent, Lower arm grand-parent, grand-grand-parent, … nodes Upper arm Hierarchical representation is known as Scene Graph Hammer Leaf node Claypool & Lindeman - WPI, CS & IMGD 28 14